Liquid polymeric phenylalkylsiloxanes



Patented Dec- 16, 1947 LIQUID POLYMERIC PHENYLALKYL I SILOXANES JamesFranklin Hyde, Corning, N. Y., assignor to Corning Glass Works, Corning,N. Y., a corporation of New York No Drawing. Application September 10,1945, Serial No. 615,505

6 Claims. (Cl. 260-607) This invention relates to new compositions ofmatter and their preparation and, more particularly, to high polymericorganosilicon liquids and methods of preparing them.

This application is a continuation-in-part of my copending applicationSerial No. 481,154, filed March 30, 1943, and assigned to the assigneeof the present invention.

Hydrolysis of hydrolyzable silanes of the general formula a CsH5S i-X:

where R is a lower alkyl radical and X is either an ethoxy or a chlorineradical, produces the corresponding silanols, thus:

L R a The phenyl alkyl silanols can be isolated as such; however, theyare readily condensed to polymeric compositions known as silicones orsilanones, thus:

Calla-SH Heat and/or the presence of alkali or acid accelerates theabove condensation.

The phenyl alkyl silicones are polymeric materials of either cyclicconfiguration as represented by Formula A above or of unbranched chainstructure as shown by Formula B. Both types of polymers may be presentin the same condensation product. Furthermore, where the startinghydrolyzable silane has ethoxy groups as the hydrolyzable constituentsthe unbranched chain polymers may have ethoxy radicals terminating oneor both ends of the chain.

In general, the products obtained by the hydrolysis of hydrolyzablephenyl alkyl silanes are low molecular weight compositions even when theconditions are optimum for promoting condensation. They consist at bestof polymers whose average number of silicon atoms per molecule is lessthan eight. The trimeric and tetrameric polymers are predominant,particularly the cyclic forms. These low molecular weight products areeither crystalline solids or thin liquids having a viscosity less than500 centistokes. It is not possible to increase their viscosityappreciably by heat alone.

For many industrial applications, hydraulic fluids, damping media,lubricants, etc., are required which have a viscosity above 1000centistokes and which will not resinify or gel when heated for prolongedperiods at high temperatures. The viscosity of the above products may beincreased by blowing air through them at elevated temperatures or bytreating them with aqueous acids of the strong type, also at elevatedtemperatures. However, both of these methods result in the removal ofsome of the organic radicals, the alkyl in the case of the air treatmentand the phenyl in the case of the acid treatment. The resulting productstherefore contain some mono-organo-substituted silicion units withintheir structures and have a tendency to increase in viscosity andfinally resinify or gel when exposed to high temperatures for prolongedperiods of time. It would be highly desirable if liquids could beprepared which had a viscosity above 1000 centistokes and which wouldremain substantially unchanged when exposed to elevated temperatures forlong times as well as possessing the ability to lubricate.

The primary object of this invention is to prepare organo-siliconcompositions which have a viscosity above 1000 centistokes; which areresistant to the effect of heat alone; and which are adapted to serve aslubricants.

Another object of the present invention is to provide methods of makingthe above compositions.

Further objects and advantages of this invention will become apparentfrom the following description and claims.

I have discovered that liquids having a viscosity above 1000 centistokesmay be prepared from the hydrolysis products of hydrolyzable phenylalkyl silanes. These liquids not only are not decomposed at temperaturesof the order of 300 C. but also do not change appreciably .n viscositywhen heated to these temperatures for many hours. They possess a highdegree of lubricity and accordingly are useful as lubricants and ashydraulic media.

These liquids are high molecular weight com- Where R is either a methylor an ethyl radical.

They may be prepared in the following manner.

A hydrolyzable organo-silane of the general formula where R. is either amethyl or an ethyl radical and X is either a chlorine or an ethoxyradical is first hydrolyzed to the corresponding monomeric silanol. Thelatter can be condensed, if desired, to a low molecular weight siloxaneby heat in the presence or absence of a condensation catalyst such asacid or alkali. A crystalline solid or a liquid of relatively lowviscosity is obtained. Either may be employed in the subsequentreaction. This silanol or low molecular weight siloxane is treated withan anhydrous alkali metal hydroxide, such as solid sodium or potassiumhydroxide at a temperature below 200 C. and preferably below 100 C. Theamount of alkali is such that the ratio of the number of silicon atomsin the silicone to the number of alkali metal atoms in the hydroxide isgreater than 10 to 1. The alkyl may be added in increments, if desired.The reaction is continued until the desired viscosity is obtained. Thealkali may then be removed by washing with acidified water until theproduct is neutral. It is then washed with water and dried. By thistreatment, if allowed to continue until no increase in viscosity isobtained, liquids are produced having little or no flow at roomtemperature.

In the above process, I have found that where liquids of the order of100,000 centistokes viscosity or higher are desired, the ratio ofsilicon atoms in the silicone to the alkali metal atoms in the hydroxideshould be between about 100 to 1 and 500 to 1. It is extremely importantin this process if high viscosity fluids of the order of 10,000centistokes viscosity or higher are to be obtained to be sure that thestarting silanes are free of other silanes such as the mono-organo ortri-organo-substituted silanes. The presence of these silanes interfereswith the production of high viscosity liquids by the above process.

Analysis of the products obtained by the above process showed them toconsist of the recurring structural unit of the formula (CoHOSIiOpolymers whose recurring unit was (CsHs) RSiO,

the chains being terminated byhydroxyl and/or ethoxyl groups. It is tobe understood, however, that some of the polymers contained in theproduct may be cyclic in conformation, the essential ingredient beingthe 'unit (CaH5)RSiO.

The average number of structural units per molecule in the product wasat least eight. It was impossible to determine accurately what theaverage molecular size was of the products having little or no flow atroom temperature.

The high polymeric liquids, namely, phenyl methyl polysilanone andphenyl ethyl polysilanone, particularly those having a viscosity between1000 and 100,000 centistokes, are eminently adapted for use as hydraulicor damping fluids, dielectric media, and as lubricants between metallicsurfaces such as steel and bronze. I have found that the presence of thephenyl radical greatly enhances the utility of the silicone aslubricants as contrasted with the dialkyl silicones. It has also beenfound advantageous to employ the high molecular weight liquids of thisinvention as intermediates for the preparation of resins by air-blowingthem at elevated temperatures. The resins so obtained possess anunusually high degree of flexibility. For a better understanding of myinvention, reference should be had to the following examples.

Example 1 A sample of phenyl ethyl silicone having a viscosity of 60centistokes was prepared by dropping phenyl ethyl silicon dichlorideinto aqueous ethyl alcohol and recovering the organo-silicone liquidformed. This liquid was treated with solid sodium hydroxide in suchamount that the atomic ratio of Si/Na was equal to 25/1. The temperaturewas held at to- C. for several hours. After washing out the alkali anddrying by subjecting to vacuum, the viscosity of the product was 5023centistokes.

Example 2 Liquid polymeric phenyl methyl silicone was treated with solidsodium hydroxide in an amount corresponding to a ratio of 50 siliconatoms to one sodium atom. The temperature of the mixture was held atabout C. for several hours until the viscosity appeared to attain aconstant value. It was then found that the silicone had increased inviscosity from an initial value of 332 centistokes to a final value ofabout 1100 centistokes after the alkali had been removed byneutralization and washing.

Example 3 Samples of phenyl ethyl silicone having a viscosity of 309centistokes were treated with powdered sodium hydroxide and potassiumhydroxide, respectively, in such amounts that the atomic ratio of Si/Nawas equal to 200/1. After 48 hours at 60 to 80 C. and after drying withvacuum, the viscosities were 2348 and 3562 centistokes, respectively.

Example 5 A sample of phenyl ethyl silicone having a viscosity of 64centistokes was treated with powdered sodium hydroxide in such amountthat the atomic ratio of Si/Na was equal to 100/1. The mixture wasstirred and heated from one to two hours at 80 to 100 C. under vacuum.After 17 days at room temperature, the viscosity of the product was10,500 centistokes.

Example 6 Phenyl ethyl silicone was prepared from phenyl ethyl silicondichloride by dropping 100 grams of the latter into 50 cc. of water atroom temperature over a period of 3 hours. After washing out the acidwith water. and finally ammonia, the final product had a viscosity of388 centistokes. A 55.8 gram sample was treated with powdered sodiumhydroxide in such amount that the atomic ratio of Si/Na was equal to300/1. Approximate- 1y 20 cc. of ether were added to the sample to helpdisperse the sodium hydroxide and the mixture was stirred at roomtemperature for 18 hours. After subsequently raising the temperaturefrom 80 to 100 C. for four to five hours and removing any remainingether under vacuum, the product had a viscosity of 15,150 centistokes.

Example 7 Phenyl ethyl silicone was prepared from phenyl ethyl silicondichloride by dropping the chloride into water at room temperature. Aliquid having Viscosity.

Time, Hours centistokes Example 8 A sample of the cyclic trimer ofphenyl ethyl silicone was treated with powdered sodium hydroxide in suchamount that the atomic ratio of Si/Na was equal to 100/1 and heated toaround 60 C. with stirring. After 24 hours the treated trimer had aviscosity of 10,920 centistokes and at 96 hours its viscosity wasapproximately 1,000,000 centistokes or 94.5 centistokes in a 50% toluenesolution. It was then dissolved in toluene and heated for an additional66 hours at 60- 70C. The product after removal of the alkali by washinghad a viscosity of 125 centistokes in a 50% toluene solution at 25 C.Removal of solvent left a material having little flow at roomtemperature.

Example 9 A 50 gram sample of phenyl ethyl silicone (viscosity 310centistokes, 2.07 %OH) was treated with powdered sodium hydroxide insuch amount that the ratio of Si/Na was equal to 100/1. The sample wasstirred at 60 C. in a rather deep layer in a test tube. After 24 hoursthe viscosity rose to 9,650 centistokes. After another 24 hours at thesame temperature, the sample was dried by placing under vacuum andwarming slightly. Its viscosity was 12,250 centistokes. Further heatingat 60 C. with stirring for 18 hours raised the viscosity to 31,200centistokes.

Example 10 Phenyl ethyl silicon dichloride was hydrolyzed by droppingslowly into enough water at room temperature to form 10% aqueous-HCl.The isolated product had a viscosity of 309 centistokes and a hydroxycontent of 3.54%. A 150 gram sample of this material was treated with.266

gram of solid sodium hydroxide in .524 gram of aqueous solution(Si/Na=l50/1) and stirred at -85 C. The viscosity rose steadily up to 48hours at which point it was 56,000 centistokes.

Example 11 To a mixture of '78 g. of ethanol, 108 g. of water and 0.6 g.of acetic acid, at 0 C., 23.0 g. of diethoxymethylphenylsilane was addeddropwise. After addition was complete, the mixture was diluted with 200ml. of water, salted and extracted with ether. From the ether extract14.9 g. of product was obtained, which on diluting with a small amountof petroleum ether and cooling, yielded 11.5 g. of crystals. Thecrystals were a mixture of the monomeric and dimeric phenyl methyldiols. Repeated recrystallizations from combinations of petroleum etherwith diethyl ether or benzene brought about some separation intofractions rich in the monomer diol (the less soluble constituent) andfractions in which the dimer diol was predominant. A fraction,containing 13.? hydroxyl, weighing 1.83 g., was mixed with 0.0111 g. ofpowdered NaOI-I, three ml. of toluene and 4 ml. of ether. The alkalireacted and dispersed in about ten minutes. Solvents were removed under15 mm. pressure at room temperature. After a day of such treatment, theresin, still under reduced pressure. was heated to 77 C. for 48 hours.It became steadily more viscous. The temperature was raised to C. for 24hours, after which the polymer was dissolved in ether, treated withacetic acid and washed to neutrality. Solvents and volatiles wereremoved under reduced pressure, leaving a thermoplastic compositionhaving little flow at room temperature.

The viscosity of a 0.5% solution in toluene was 0.73 centistokes whichcorresponds to an intrinsic viscosity of 2.40. Even higher intrinsicviscosities may be obtained by continuing the above treatment for alonger period of time.

Example 12 To liquid polymeric phenyl ethyl silicone havin a viscosityof 412 centistokes was added solid sodium hydroxide in an amountcorresponding to a ratio of 100 silicon atoms to one sodium atom. Themixture was held at a temperature of about C. for several hours. Theproduct had a viscosity of over 20,000 centistokes. After beingneutralized and washed, the product was applied to glass fibre tape andheated in air at 200 C. for 8 hours, and for 5 hours at 250 C. Aresinous coating was produced which was tack-free and flexible.

I claim:

1. An organo-polysiloxane consisting essentially of the recurringstructural unit corresponding to the formula (CsH5)RSiO where R isselected from the class consisting of methyl and ethyl radicals, therebeing on the average at least eight of said units per molecule, saidpolysiloxane having a. viscosity greater than 1000 centistokes and beingfree of monoorgano and triorgano-substituted silicon units.

2. An organo-polysiloxane consisting essential- 1y of the recurringstructural unit corresponding to the formula (CsH5)RSiO where R isselected from the class consisting of methyl and ethyl radicals, therebeing on the average at least eight of said units per molecule, saidpolysiloxane having a viscosity between 1000 and 100,000 centistokes andbeing free of monoorganoand triorgano-substituted silicon units.

3. A phenyl methyl polysiloxane consisting essentially of the recurringstructural unit corresponding to the formula (CsHc)-(CHs)SiO, therebeing on the average at least eight of said units per molecule, saidpolysiloxane having a viscosity greater than 1000 centistokes and beingfree of monoorganoand triorgano-substituted silicon units.

4. A phenyl methyl polysiloxane consisting essentially of the recurringstructural unit corresponding to the formula (Cal-I5) (CI-1:)Si0, therebeing on the average at least eight of said units per molecule, saidpolysiloxane having a viscosity between 1000 and 100,000 centistokes andbeing free of monoorganoand triorgano-substituted silicon units.

5. A phenyl ethyl polysiloxane consisting essentially of the recurringstructural unit corresponding to the formula (Cells) (C2H5)S10, therebeing on the average at least eight of said units per molecule, saidpolysiloxane having a viscosity greater than 1000 centistokes and beingfree of monoorganoand triorgano-substituted silicon units.

6. A phenyl ethyl polysiloxane consisting essen- REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,258,222 Rochow Oct. 7, 1941FOREIGN PATENTS Number Country Date 113,708 Australia Sept. 4, 1941OTHER REFERENCES Robison et al., Jour. Chem. Soc. (London), vol. 101(1912), p. 2159.

